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 Monday, 20 January, 2003, 23:42 GMT
Great uncle aardvark?
Aardvark (Proceedings of the National Academy of Sciences)
Our ancient ancestor may have had something in common with the aardvark
The ancient ancestor of all mammals that give birth to live young - including humans - probably had genetic similarities with the aardvark.

The elusive African mammal is a close match to our early cousin in the way its DNA is packaged into distinct bundles, or chromosomes, say scientists.

All mammals essentially had one common ancestor if you go back in distant time

Prof Terence Robinson
The last common ancestor of all placental mammals - possibly a shrew-like creature - scurried over the planet hundreds of millions of years ago.

It was probably nothing like the modern-day aardvark but could have had a similar set of chromosomes.

Jumbo cousin

The aardvark, which feeds on ants and termites, is something of a genetic oddity.

It looks nothing like an elephant but has been lumped in with jumbo and co when it comes to its genetic make-up.

Many scientists think both are members of the group from which all placental mammals evolved.

The aardvark
Also known as the ant bear or earth pig
Inhabit Africa, south of the Sahara
Nocturnal and solitary, it hides in burrows up to 10m long
The order of mammals - known as Afrotherians - arose in Africa at a time when the continent was isolated from the rest of land by the movement of the Earth's plates.

Six animals - the aardvark, elephant, hyrax, manatee, elephant shrew and golden mole - belong to the group, on the basis of their genetic sequences.

The last common ancestor of all placental mammals - including humans - may also have been a member of the group.

The aardvark appears to be the closest match to this ancient relative in terms of how little its DNA has changed over time.

Deck of cards

Professor Terence Robinson of the University of Stellenbosch, near Cape Town, South Africa, is author of the study, published in the Proceedings of the National Academy of Sciences.

He told BBC News Online: "All mammals essentially had one common ancestor if you go back in distant time.

"By looking at the chromosomes of living species and extrapolating backwards, the aardvark seems to have retained a large number of primitive chromosomal characteristics."

The analysis is based on how much the chromosomes of related animals change over time during the process of evolution.

Co-author Professor Malcolm Ferguson-Smith of the University of Cambridge, UK, describes this as a bit like "shuffling a deck of cards".

For some reason, as yet unknown, the chromosomes of the aardvark have undergone "very few shuffles" since the last common ancestor of all placental mammals walked the Earth.

"The animal seems to have conserved the ancestral karyotype [number and form of the chromosomes of an organism] in a way that other mammals haven't," he said.

What is clear is that we are "not in the least bit like aardvarks". However, like all mammals that bear live young, we once shared a common bond.

Image courtesy of the Proceedings of the National Academy of Sciences.

See also:

24 May 01 | Science/Nature
24 Apr 02 | Science/Nature
14 Nov 00 | Science/Nature
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